Radio Communication Method, Radio Communication System and Wireless Terminal

1. A method of communicating in a multihop radio network including a plurality of wireless terminals, the method comprising: at a first wireless terminal, one of increasing and decreasing an intermittent receive period of the first wireless terminal based on a characteristic of the multihop radio network; and at a second wireless terminal, in response to the one of increasing and decreasing said intermittent receive period of the first wireless terminal, increasing a preamble length of data to be sent by the second wireless terminal to the first wireless terminal corresponding to the changed intermittent receive period if the intermittent receive period is increased, and decreasing the preamble length of data corresponding to the changed intermittent receive period if the intermittent receive period is decreased.

2. The method claimed in claim 1 , wherein the characteristic comprises at least one of a change in traffic volume on the multihop radio network, a network topology change, a time change, remaining battery power of the plurality of wireless terminals, and an occurrence of an event.

3. The method claimed in claim 2 , wherein one wireless terminal as a base station monitors the traffic volume, and if the monitored volume of traffic is larger than a predetermined upper limit value, the intermittent receive period and the preamble length of data of the plurality of wireless terminals are shortened and, if the monitored volume of traffic is smaller than a predetermined lower limit value, the intermittent receive period and the preamble length of data of the plurality of wireless terminals are extended.

4. The method claimed in claim 2 , wherein if the volume of traffic received by the first wireless terminal from the second wireless terminal is larger than a predetermined upper limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are shortened and, if the volume of traffic received by the first wireless terminal from the second wireless terminal is smaller than a predetermined lower limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are extended.

5. The method claimed in claim 2 , wherein if the volume of traffic sent from the second wireless terminal to the first wireless terminal is larger than a predetermined upper limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are shortened and, if the volume of traffic sent from the second wireless terminal to the first wireless terminal is smaller than a predetermined lower limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are extended.

6. The method claimed in claim 2 , wherein one wireless terminal as a base station detects a topology change of the multihop radio network, and if an expected volume of traffic based on the detected topology change is larger than a predetermined upper limit value, the intermittent receive period and the preamble length of data of the plurality of wireless terminals are shortened and, if the expected volume of traffic based on the detected topology change is smaller than a predetermined lower limit value, the intermittent receive period and the preamble length of data of the plurality of wireless terminals are extended.

7. The method claimed in claim 2 , wherein if an expected volume of traffic to be received by the first wireless terminal from the second wireless terminal based on a topology change of the multihop radio network is larger than a predetermined upper limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are shortened and, if the expected volume of traffic to be received by the first wireless terminal from the second wireless terminal based on the topology change is smaller than a predetermined lower limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are extended.

8. The method claimed in claim 2 , wherein if an expected volume of traffic to be sent from the second wireless terminal to the first wireless terminal based on a topology change of the multihop radio network is larger than a predetermined upper limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are shortened and, if the expected volume of traffic to be sent from the second wireless terminal to the first wireless terminal based on the topology change is smaller than a predetermined lower limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are extended.

9. The method claimed in claim 2 , wherein one wireless terminal as a base station detects the time change and, at a predetermined time, the intermittent receive period and the preamble length of data of the plurality of wireless terminals are changed.

10. The method claimed in claim 2 , wherein the plurality of wireless terminals detect the time change and, at a predetermined time, and change the intermittent receive period and the preamble length of data of the plurality of wireless terminals.

11. The method claimed in claim 2 , wherein if an expected volume of traffic to be received by the first wireless terminal from the second wireless terminal based on the time change is larger than a predetermined upper limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are shortened and, if the expected volume of traffic to be received by the first wireless terminal from the second wireless terminal based on the time change is smaller than a predetermined lower limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are extended.

12. The method claimed in claim 2 , wherein if an expected volume of traffic to be sent from the second wireless terminal to the first wireless terminal based on the time change is larger than a predetermined upper limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are shortened and, if the expected volume of traffic to be sent from the second wireless terminal to the first wireless terminal based on the time change is smaller than a predetermined lower limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are extended.

13. The method claimed in claim 2 , wherein the second wireless terminal detects the occurrence of an event, and if an expected volume of traffic to be sent from the second wireless terminal to the first wireless terminal based on the occurrence of the detected event is larger than a predetermined upper limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are shortened and, if the expected volume of traffic to be sent from the second wireless terminal to the first wireless terminal based on the occurrence of the detected event is smaller than a predetermined lower limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are extended.

14. The method claimed in claim 2 , wherein the plurality of wireless terminals inform one wireless terminal as a base station of their remaining battery power, and the base station changes the intermittent receive period and the preamble length of data of the plurality of wireless terminals based on the remaining battery power.

15. The method claimed in claim 2 , wherein the first wireless terminal detects a battery remaining power in the first wireless terminal, and if the detected remaining battery power is larger than a predetermined upper limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are shortened and, if the detected remaining battery power is smaller than a predetermined lower limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are extended.

16. The method claimed in claim 2 , wherein one wireless terminal monitors at least one of the time change, a change in topology of the multihop radio network, and a change in received traffic of the multihop radio network, a change in transmitted traffic of the multihop radio network, the occurrence of the event and the remaining battery power of the plurality of wireless terminals, and determines the intermittent receive period and the preamble length of data of each of the plurality of wireless terminals based on the monitoring.

17. The method claimed in claim 1 , wherein the plurality of wireless terminals are connected in a tree or mesh structure.

18. The method claimed in claim 1 , wherein a receiving side of each of the plurality of wireless terminals is activated during the intermittent receive period, and wherein the receiving side is deactivated when not receiving a signal during the intermittent receive period.

19. The method claimed in claim 1 , wherein the preamble length of data to be sent by the second wireless terminal to the first wireless terminal is greater than the intermittent receive period of the first wireless terminal.

20. The method claimed in claim 1 , wherein if the intermittent receive period is increased, an increase of the preamble length of data matches an increase of the intermittent receive period and if the intermittent period is decreased, a decrease of the preamble length of data matches a decrease of the intermittent receive period.

21. A radio communication system of a multihop radio network including a plurality of wireless terminals, the system comprising: a first wireless terminal comprising: network characteristics detecting means for detecting a characteristic of the multihop radio network; and intermittent receive period setting means for setting an intermittent receive period of the first wireless terminal based on the characteristic detected by the network characteristics detecting means; and a second wireless terminal including preamble length changing means for increasing a preamble length of data to be sent by the second wireless terminal to the first wireless terminal corresponding to the intermittent receive period set by the intermittent receive period setting means if the intermittent receive period of the first wireless terminal is increased, and for decreasing the preamble length of data corresponding to the changed intermittent receive period if the intermittent receive period of the first wireless terminal is decreased, wherein if the network characteristics detecting means detects a change of the characteristic of the multihop radio network, the intermittent receive period setting means changes the intermittent receive period of the first wireless terminal, and the preamble length changing means changes the preamble length of data of the second wireless terminal in response to the intermittent receive period setting means changing the intermittent receive period of the first wireless terminal.

22. The radio communication system claimed in claim 21 , wherein the characteristic comprises at least one of a change in traffic volume on the multihop radio network, a network topology change, a time change, remaining battery power of the plurality of wireless terminals, and an occurrence of an event.

23. The radio communication system claimed in claim 21 , wherein the preamble length of data to be sent by the second wireless terminal to the first wireless terminal is greater than the intermittent receive period of the first wireless terminal.

24. The radio communication system claimed in claim 21 , wherein if the intermittent receive period is increased, an increase of the preamble length of data increased by the preamble length changing means matches an increase of the intermittent receive period, and if the intermittent receive period is decreased, a decrease of the preamble length of data decreased by the preamble length changing means matches a decrease of the intermittent receive period.

25. The radio communication system claimed in claim 22 , wherein one wireless terminal as a base station comprises: a monitoring means for monitoring the traffic volume of the multihop radio network; a determining means for determining the intermittent receive period and the preamble length of data of the plurality of wireless terminals based on the traffic volume monitored by the monitoring means; and an informing means for informing the plurality of wireless terminals of the intermittent receive period and the preamble length of data determined by the determining means; and wherein each of the plurality of wireless terminals include receiving means for receiving the information on the intermittent receive period and the preamble length of data from the base station, and the plurality of wireless terminals change their intermittent receive period and their preamble length of data based on the information received by the receiving means.

26. The radio communication system claimed in claim 22 , wherein the first wireless terminal further includes measuring means for measuring a volume of data traffic received by the first wireless terminal from the second wireless terminal, and if the measured volume of data traffic is larger than a predetermined upper limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are shortened and, if the measured volume of data traffic received by the first wireless terminal from the second wireless terminal is smaller than a predetermined lower limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are extended.

27. The radio communication system claimed in claim 22 , wherein the second wireless terminal further includes measuring means for measuring a volume of data traffic sent by the second wireless terminal to the first wireless terminal, and if the measured volume of traffic is larger than a predetermined upper limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are shortened and, if the measured volume of data traffic sent by the second wireless terminal to the first wireless terminal is smaller than a predetermined lower limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are extended.

28. The radio communication system claimed in claim 22 , wherein one wireless terminal as a base station further includes: a detecting means for detecting a topology change of the multihop radio network; a predicting means for predicting the traffic on the multihop radio network based on the topology change detected by the detecting means; a determining means for determining the intermittent receive period and the preamble length of data of the plurality of wireless terminals based on the traffic predicted by the predicting means; and an informing means for informing the plurality of wireless terminals of the intermittent receive period and the preamble length of data determined by the determining means, wherein each of the plurality of wireless terminals includes receiving means for receiving the information on the intermittent receive period and the preamble length of data from the base station, and the plurality of wireless terminals change their intermittent receive period and their preamble length based on the information received by the receiving means.

29. The radio communication system claimed in claim 22 , wherein the first wireless terminal further includes: detecting means for detecting a topology change of the multihop radio network; and predicting means for predicting a volume of traffic received by the first wireless terminal from the second wireless terminal based on the topology change detected by the detecting means, and if the volume of traffic predicted by the predicting means is larger than a predetermined upper limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are shortened and, if the predicted volume of traffic received by the first wireless terminal from the second wireless terminal based on the topology change is smaller than a predetermined lower limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are extended.

30. The radio communication system claimed in claim 22 , wherein the second wireless terminal further comprises: a detecting means for detecting a topology change of the multihop radio network; and a predicting means for predicting a volume of traffic sent from the second wireless terminal to the first wireless terminal based on the topology change detected by the detecting means, and if the volume of traffic predicted by the predicting means is larger than a predetermined upper limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are shortened and, if the predicted volume of traffic sent from the second wireless terminal to the first wireless terminal based on the topology change is smaller than a predetermined lower limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are extended.

31. The radio communication system claimed in claim 22 , wherein one wireless terminal as a base station further comprises: a clock means for obtaining a time; a determining means for determining the intermittent receive period and the preamble length of data of the plurality of wireless terminals based on the time obtained by the clock means; and an informing means for informing the plurality of wireless terminals of the intermittent receive period and the preamble length of data determined by the determining means, wherein each of the plurality of wireless terminals include receiving means for receiving the information on the intermittent receive period and the preamble length of data from the base station, and the plurality of wireless terminals change their intermittent receive period and their preamble length based on the change information received by the receiving means.

32. The radio communication system claimed in claim 22 , wherein each of the plurality of wireless terminals further comprise: a clock means for obtaining a time; and a determining means for determining the intermittent receive period and the preamble length of data of the wireless terminal based on the time obtained by the clock means.

33. The radio communication system claimed in claim 22 , wherein the first wireless terminal further comprises: a clock means for obtaining a time; a predicting means for predicting a volume of traffic received by the first wireless terminal from the second wireless terminal which varies according to the time obtained by the clock means; and an expecting means for predicting the volume of traffic received by the first wireless terminal from the second wireless terminal, and if the volume of traffic predicted by the expecting means is larger than a predetermined upper limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are shortened and, if the predicted volume of traffic received by the first wireless terminal from the second wireless terminal is smaller than a predetermined lower limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are extended.

34. The radio communication system claimed in claim 22 , wherein the second wireless terminal further comprises: a clock means for obtaining a time; a predicting means for predicting a volume of traffic sent from the second wireless terminal to the first wireless terminal which varies according to the time obtained by the clock means; and an expecting means for expecting the volume of traffic sent from the second wireless terminal to the first wireless terminal, and if the volume of expected traffic is larger than a predetermined upper limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are shortened and, if the expected volume of traffic sent from the second wireless terminal to the first wireless terminal is smaller than a predetermined lower limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are extended.

35. The radio communication system claimed in claim 22 , wherein the second wireless terminal further comprises: a detecting means for detecting the occurrence of an event; and predicting means for predicting a volume of traffic to be sent from the second wireless terminal to the first wireless terminal based on the occurrence of the event detected by the detecting means, and if the predicted volume of traffic to be sent from the second wireless terminal to the first wireless terminal based on the occurrence of the event is larger than a predetermined upper limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are shortened and, if the predicted volume of traffic to be sent from the second wireless terminal to the first wireless terminal based on the occurrence of the event is smaller than a predetermined lower limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are extended.

36. The radio communication system claimed in claim 22 , wherein each of the plurality of wireless terminals further comprise: a detecting means for detecting a remaining battery power of the wireless terminal; and a determining means for determining the intermittent receive period and the preamble length of the wireless terminals according to the detected remaining battery power.

37. The radio communication system claimed in claim 22 , wherein the first wireless terminal further includes a detecting means for detecting a remaining battery power of the first wireless terminal, and if the detected remaining battery power is larger than a predetermined upper limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are shortened and, if the detected remaining battery power is smaller than a predetermined lower limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are extended.

38. The radio communication system claimed in claim 22 , wherein each of the plurality of wireless terminals further comprises: a monitoring means for monitoring at least one of the time change, the network topology change of the multihop radio network, traffic received by the multihop radio network, traffic transmitted by the multihop radio network, the occurrence of the event, and remaining battery power of one or more the plurality of wireless terminals; a monitor information sending means for sending information monitored by the monitoring means to a specific wireless terminal as change information; and a setting information receiving means for receiving information on at least one of an intermittent receive period and a preamble length of data from the specific wireless terminal, wherein the specific wireless terminal includes: change information receiving means for receiving the change information from each of the plurality of wireless terminals; and determining means for determining setting information on at least one of the intermittent receive period and the preamble length of data of each of the plurality of wireless terminals based on the received change information; and setting information sending means for sending the setting information to each wireless terminal, and wherein each of the plurality of wireless terminals sets the intermittent receive period and the preamble length of data based on the received setting information.

39. A wireless terminal constituting a radio communication system of a multihop radio network including a plurality of wireless terminals, the wireless terminal comprising: a network characteristics detecting means for detecting a characteristic of the multihop radio network; an intermittent receive period setting means for setting an intermittent receive period of the wireless terminal; and preamble length changing means for increasing a preamble length of data to be sent by the wireless terminal to another wireless terminal corresponding to the set intermittent receive period of the wireless terminal if the intermittent receive period is increased, and for decreasing the preamble length of data corresponding to the set intermittent receive period if the intermittent receive period of the wireless terminal is decreased, wherein if the network characteristics detecting means detects a change of the characteristic of the network, the intermittent receive period setting means changes the intermittent receive period, and the preamble changing means changes the preamble length of data in response to the intermittent receive period setting means changing the intermittent receive period.

40. The wireless terminal claimed in claim 39 , wherein the characteristic comprises at least one of a change in traffic volume on the multihop radio network, a network topology change, a time change, remaining battery power of the plurality of wireless terminals, and an occurrence of an event.

41. The wireless terminal claimed in claim 39 , wherein preamble length of data to be sent by the wireless terminal to the other wireless terminal is greater than the set intermittent receive period.

42. The wireless terminal claimed in claim 39 , wherein if the intermittent receive period is increased, an increase of the preamble length of data increased by the preamble length changing means matches an increase of the intermittent receive period, and if the intermittent receive period is decreased, a decrease of the preamble length of data decreased by the preamble length changing means matches a decrease of the intermittent receive period.

43. The wireless terminal claimed in claim 40 further comprising: a monitoring means for monitoring the volume of traffic on the multihop radio network; a determining means for determining the intermittent receive period and the preamble length of data of the plurality of wireless terminals based on the volume of traffic monitored by the monitoring means; and informing means for informing the plurality of wireless terminals of the intermittent receive period and the preamble length of data determined by the determining means.

44. The wireless terminal claimed in claim 43 further comprising: a detecting means for detecting a topology change of the multihop radio network; a predicting means for predicting traffic volume based on the topology change detected by the detecting means; a determining means for determining the intermittent receive period and the preamble length of data of the plurality of wireless terminals based on the traffic predicted by the predicting means; and an informing means for informing the plurality of wireless terminals of the intermittent receive period and the preamble length of data determined by the determining means.

45. The wireless terminal claimed in claim 44 further comprising: a clock means for obtaining a time; a determining means for determining the intermittent receive period and the preamble length of data of the plurality of wireless terminals based on the time obtained by the clock means; and an informing means for informing the plurality of wireless terminals of the intermittent receive period and the preamble length of data determined by the determining means.

46. The wireless terminal claimed in claim 44 further comprising: a receiving means for receiving information on a remaining battery power of another wireless terminal from the other wireless terminal; a determining means for determining the intermittent receive period and the preamble length of data of the plurality of wireless terminals based on the remaining battery power of the other wireless terminal; and an informing means for informing the plurality of wireless terminals of the intermittent receive period and the preamble length of data determined by the determining means.

47. The wireless terminal claimed in claim 44 further comprising: a receiving means for receiving information on the occurrence of an event from another wireless terminal; a determining means for determining the intermittent receive period and the preamble length of data of the plurality of wireless terminals based on the occurrence of the event informed by the other wireless terminal; and an informing means for informing the plurality of wireless terminals of the intermittent receive period and the preamble length of data determined by the determining means.

48. The wireless terminal claimed in claim 44 further comprising a receiving means for receiving information on the intermittent receive period and the preamble length of data from another wireless terminal, wherein each of the plurality of wireless terminals change their intermittent receive period and their preamble length based on the received information.

49. The wireless terminal claimed in claim 48 further comprising a detecting means for detecting at least one of the change in traffic volume, the network topology change, the remaining battery power of the plurality of wireless terminals, and the occurrence of the event, and informing the plurality of wireless terminals of the information detected by the detecting means.

50. The wireless terminal claimed in claim 44 further comprising a preamble length change requesting means for requesting the plurality of wireless terminals to change their preamble length of data according to the change of the intermittent receive period.

51. The wireless terminal claimed in claim 44 further comprising an intermittent receive period change requesting means for requesting the plurality of wireless terminals to change their intermittent receive period according to the change of the preamble length of data.

52. The wireless terminal claimed in claim 44 further comprising a receiving means for receiving a preamble length change request from another wireless terminal, and wherein the wireless terminal changes the preamble length of data of the wireless terminal based on the received preamble length change request.

53. The wireless terminal claimed in claim 44 further comprising a receiving means for receiving an intermittent receive period change request from another wireless terminal, and wherein the wireless terminal changes the intermittent receive period of the wireless terminal on the basis of the received intermittent receive period change request.

54. The wireless terminal claimed in claim 44 further comprising a measuring means for measuring a volume of traffic received by the wireless terminal, and if the received volume of traffic is larger than a predetermined upper limit value, the intermittent receive period of the wireless terminal is shortened and, if the received volume of traffic is smaller than a predetermined lower limit value, the intermittent receive period of the wireless terminal is extended.

55. The wireless terminal claimed in claim 44 further comprising a measuring means for measuring a volume of traffic transmitted by the wireless terminal, and if the volume of traffic transmitted by the wireless terminal is larger than a predetermined upper limit value, the preamble length of data of the wireless terminal is shortened and, if the volume of traffic is smaller than a predetermined lower limit value, the preamble length of data of the wireless terminal is extended.

56. The wireless terminal claimed in claim 44 further comprising a detecting means for detecting a topology change of the multihop radio network and a predicting means for predicting the volume of traffic received by the wireless terminal based on the topology change, and if the predicted volume of traffic is larger than a predetermined upper limit value, the intermittent receive period of the wireless terminal is shortened and, if the volume of traffic is smaller than a predetermined lower limit value, the intermittent receive period of the wireless terminal is extended.

57. The wireless terminal claimed in claim 44 further comprising a detecting means for detecting a topology change of the multihop radio network and a predicting means for predicting a volume of traffic transmitted by the wireless terminal based on the topology change, and if the predicted volume of traffic is larger than a predetermined upper limit value, the preamble length of data of the wireless terminal is shortened and, if the predicted volume of traffic is smaller than a predetermined lower limit value, the preamble length of data of the wireless terminal is extended.

58. The wireless terminal claimed in claim 44 further comprising a clock means for obtaining a time and a predicting means for predicting a volume of traffic received by the wireless terminal based on the time change, and if the predicted volume of traffic is larger than a predetermined upper limit value, the intermittent receive period of the wireless terminal is shortened and, if the predicted volume of traffic is smaller than a predetermined lower limit value, the intermittent receive period of the wireless terminal is extended.

59. The wireless terminal claimed in claim 44 further comprising a clock means for obtaining a time and a predicting means for predicting a volume of traffic transmitted by the wireless terminal based on the time change, and if the predicted volume of traffic is larger than a predetermined upper limit value, the preamble length of data of the wireless terminal is shortened and, if the volume of traffic is smaller than a predetermined lower limit value, the preamble length of data of the wireless terminal is extended.

60. The wireless terminal claimed in claim 44 further comprising a detecting means for detecting the occurrence of an event and a predicting means for predicting the volume of traffic to be sent from a first wireless terminal to a second wireless terminal based on the occurrence of the detected event, and if the predicted volume of traffic is larger than a predetermined upper limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are shortened and, if the predicted volume of traffic is smaller than a predetermined lower limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are extended.

61. The wireless terminal claimed in claim 44 further comprising a detecting means for detecting a remaining battery power of another wireless terminal, and if the detected remaining battery power is larger than a predetermined upper limit value, the intermittent receive period of a first wireless terminal and the preamble length of data of a second wireless terminal are shortened and, if the detected remaining battery power is smaller than a predetermined lower limit value, the intermittent receive period of the first wireless terminal and the preamble length of data of the second wireless terminal are extended.

62. The wireless terminal claimed in claim 44 further comprising a receiving means for receiving information on at least one of the intermittent receive period of the wireless terminal and the preamble length of data of the wireless terminal from a specific wireless terminal, and wherein the wireless terminal changes at least one of the intermittent receive period of the wireless terminal and the preamble length of the wireless terminal based on the information received from the specific wireless terminal.

63. The wireless terminal claimed in claim 62 further comprising a monitoring means for monitoring at least one of the time change, the network topology change of the multihop radio network, traffic received by the multihop radio network, traffic transmitted by the multihop radio network, the occurrence of the event and remaining battery power of one or more of the plurality of wireless terminals, and a sending means for sending the information monitored by the monitoring means to the specific wireless terminal.

64. The wireless terminal claimed in claim 44 further comprising a determining means for determining setting information on at least one of the intermittent receive period and the preamble length of the plurality of wireless terminals except the wireless terminal itself and a sending means for sending the setting information to the plurality of wireless terminals except the wireless terminal itself.

65. The wireless terminal claimed in claim 44 further comprising: a receiving means for receiving information on at least one of the network topology of the multihop radio network, traffic received by the multihop radio network, traffic transmitted by the multihop radio network, the occurrence of the event and remaining battery power of the plurality of wireless terminals except the wireless terminal itself; and a determining means for determining setting information on at least one of the intermittent receive period and the preamble length of data of each of the plurality of wireless terminals based on the information received by the receiving means; and a sending means for sending the setting information to the plurality of wireless terminals.